Stress analysis of a Burch-Schneider cage in an acetabular bone defect: A case study

Burch-Schneider cages are often used for the treatment of acetabular bone defects. In several clinical studies these cages have shown good mid- to long-term results. However, a higher failure rate has been reported in large Paprosky IIIB defects compared with smaller Paprosky II-IIIA defects. This study aims to investigate the effect of cage support on cage failure by means of finite element analysis. The Von Mises stresses in both the implant and the bone are analyzed for a Burch-Schneider cage used in the following scenarios: (1) a large acetabular bone defect, (2) a small acetabular bone defect and (3) a large acetabular bone defect in combination with a reinforcement plate. The results show that implant and bone stresses are higher in the large defect (99 th percentile of 146.6 and 73.5 MPa respectively) than in the small defect (99 th percentile of 43.9 and 47.9 MPa respectively). Adding a reinforcement plate to posteriorly support the cage decreases the stresses but not fully compensates for the missing bone support (99 th percentile of 93.1 and 55.3 MPa respectively). Since high stresses cause an increased risk for fatigue failure and implant loosening, sufficient implant support is required to reduce the risk of cage failure.